Method for controlling a semiconductor bridge of an electrically operable motor by means of a ramp signal, control device and arrangement

ABSTRACT

A method for controlling a semiconductor bridge of an electrically operable motor, the semiconductor bridge being controlled depending on a pulse width modulation signal by a first controllable semiconductor switch and a separate second controllable semiconductor switch for supplying the electrically operable motor with electrical energy, a ramp signal with a predeterminable ramp slope for controlling one of the two controllable semiconductor switches being generated by a ramp generator, depending on the pulse width modulation signal. The invention also relates to a control device and to an arrangement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase Application of PCTInternational Application No. PCT/EP2018/076628, filed Oct. 1, 2018,which claims priority to German Patent Application No. 10 2017 218305.5, filed Oct. 13, 2017, the contents of such applications beingincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a method for controlling a semiconductor bridgeof an electrically operable motor, the semiconductor bridge beingcontrolled depending on a pulse width modulation signal by a firstcontrollable semiconductor switch and a separate second controllablesemiconductor switch for supplying the electrically operable motor withelectrical energy. The motor may in particular be an electricallyoperable motor for use in a motor vehicle, which is used for example asan adjusting motor in a window lifter mechanism, for a door release or aseat adjustment mechanism. The invention also relates to a controldevice and an arrangement.

BACKGROUND OF THE INVENTION

DC motors, which are used for example in motor vehicles, are usuallycontrolled by means of relays or semiconductors. If variable control ofthe electrically operable motor is required, the semiconductors, whichmay for example be a MOSFET or an IGBT, are controlled by means of pulsewidth modulation. The switches are in this case switched on or offperiodically to achieve the required power. The switching process is inthis case dependent in particular on the parameters of the semiconductorand the arrangement, as a result of which tolerances in the switchingtime or switching slope must be taken into account, in particular if thecontrol current is kept low in order to achieve high electromagneticcompatibility for the switching speed. A result of this is that thedegree of sampling of the pulse width modulation control changessignificantly, and in particular a short-circuit detection andprotective devices for the switches can only react late to a shortcircuit. This means that the switches do not operate reliably.

EP 1986322 B1, incorporated herein by reference, also discloses anoutput stage for pulse-width-modulated activation of an electrical load.The output stage comprises a first input for inputting a first pulsewidth modulation signal, a power semiconductor switch for activating theelectrical load in accordance with the duty cycle of the first pulsewidth modulation signal, and a delay circuit for generating a secondpulse width modulation signal that is delayed compared to the firstpulse width modulation signal, and a signal output for outputting thesecond pulse width modulation signal. The delay circuit comprises afirst detector circuit, which determines the period of the first pulsewidth modulation signal and generates the second pulse width modulationsignal such that it is delayed by a fraction of the determined periodduration determined by a control signal compared to the first pulsewidth modulation signal. The disadvantage of such as pulse-to-pulsemodulation is that the regulating device must be very complex and thatafter each start-up of the regulator a corresponding run-up time isrequired, which means that there is a period in which the switching isnot reliably provided.

SUMMARY OF THE INVENTION

An aspect of the present invention is a method, a control device and anarrangement by means of which a switching speed of the semiconductorbridge is independent of the MOSFETs used and has improvedelectromagnetic compatibility.

One aspect of the invention relates to a method for controlling asemiconductor bridge of an electrically operable motor, thesemiconductor bridge being controlled depending on a pulse widthmodulation signal by a first controllable semiconductor switch and aseparate second controllable semiconductor switch for supplying theelectrically operable motor with electrical energy.

Depending on the pulse width modulation signal, a ramp signal with apredeterminable ramp slope for controlling one of the two controllablesemiconductor switches is generated by means of a ramp generator.

As a result, the gate of the MOSFET can be activated independently ofthe type of parameter values of the MOSFET, so that the switching speedof the semiconductor bridge can be controlled independently of theMOSFETs used. Furthermore, the switching of the semiconductor bridge canbe carried out with improved electromagnetic compatibility as a resultof the predeterminable controlled ramp slope. Furthermore, the gateruntime can be shortened and stabilized by means of the method, inparticular under operating conditions. An improved duty cycle of thepulse width modulation signal can also be realized from the shortenedand stable gate delay. This also allows improved monitoring as towhether the respective semiconductor switch has switched or not to becarried out. Furthermore, the precontrol can be used to make theswitching of the semiconductor bridge insensitive to interference at theelectrical outputs without feedback.

The electrically operable motor is in particular an electricallyoperable motor of a motor vehicle. For example, the electricallyoperable motor can be an adjustment motor in the motor vehicle. A windowlifter motor or a door release motor or a seat adjustment motor can bementioned as an example of the electrically operable motor. Inparticular, such an adjustment motor requires a variable control, sothat different powers can be transmitted to the adjustment motor.Different settings of the electric motor can thus be realized. Thesemiconductor bridge thus controls in particular the electrical energyas the supply voltage for the electrically operable motor, in particularfor the adjustment motor in the motor vehicle. The electrically operablemotor is in particular an electrically operable motor which can beoperated by means of a direct current.

In the following explanations, it is assumed that the controllablesemiconductor switches are closing switches, so that, if the gates arenot supplied, the controllable semiconductor switches are open and aretherefore non-conductive.

It is likewise possible that the controllable semiconductor switches aredesigned as make contacts, as a result of which the method explainedbelow changes only on the basis of the corresponding parameter values ofthe controls.

According to an advantageous embodiment, the ramp signal for apredetermined opening value can represent an opening signal for thefirst controllable semiconductor switch and a closing signal for thesecond controllable semiconductor switch when the first controllablesemiconductor switch is open. In particular, it may be provided that theopening value is for example 0 volts, so that, when the ramp signalreaches 0 volts, the first controllable semiconductor switch is opened.In particular, only when the first controllable semiconductor switch isopen is the second controllable semiconductor switch closed. This canprevent a short circuit in the semiconductor bridge.

It has also proven to be advantageous if the ramp signal is generated bythe ramp generator with a predetermined fall time, so that the closingsignal for the second controllable semiconductor switch is at least onlygenerated after the fall time. In particular, the voltage of the rampsignal drops linearly within the predeterminable fall time. When thevoltage of the ramp signal drops, the supply voltage of the electricallyoperable motor also automatically drops in a ramp-like manner. Inparticular, an exact point in time at which the second controllablesemiconductor switch is closed can be determined by the predeterminedfall time of the ramp signal for the first controllable semiconductorswitch. An improved and more reliable control of the semiconductorbridge can thus be realized.

It is likewise advantageous if the closing signal for the secondcontrollable semiconductor switch is only generated after the fall timeand after a predetermined fade-out time. A time buffer can thereby becreated, so that it can be ensured that, when the second controllablesemiconductor switch is closed, the first controllable semiconductorswitch is open. A short circuit of the supply voltage can thus bereliably prevented.

It is also advantageous if an opening signal for the second controllablesemiconductor switch is generated when there is a predetermined openingvalue of the pulse width modulation signal and a closing signal for thefirst controllable semiconductor switch is generated when the secondcontrollable semiconductor switch is open. If for example the pulsewidth modulation signal jumps to a logical 1, this may for examplerepresent the opening signal for the second controllable semiconductorswitch. Only when the second controllable semiconductor switch iscompletely open is the first controllable semiconductor switch closed,so that a short circuit of the supply voltage can be reliably prevented.

According to a further advantageous embodiment, the ramp signal for thefirst controllable semiconductor switch can be generated with apredetermined rise time when the second controllable semiconductorswitch is open. In other words, when the second controllablesemiconductor switch is completely open, the ramp signal is applied tothe first controllable semiconductor switch, so that the supply voltagelikewise rises in a ramp-like manner. As a result, even when the firstcontrollable semiconductor switch is closing, the switching process canbe reliably carried out independently of the type of semiconductorswitches used. In particular, this can improve the switching speed ofthe semiconductor bridge. Furthermore, the electromagnetic compatibilitycan also be increased when the first controllable semiconductor switchis closing. This allows reliable control of the semiconductor bridge forsupplying the electrically operable motor to be realized.

It is also advantageous if the ramp signal is amplified by means of avoltage follower. The voltage follower is in particular an amplifierwith a voltage gain of one, in the case of which in particular only thecurrent is amplified. Improved operation of the semiconductor bridge canthereby be realized, since sufficient current can be made available forcontrolling the semiconductor switch even under load.

It has also proven to be advantageous if the fall time and/or the risetime, which are in particular linear, of the ramp signal and/or thefade-out time is predetermined by means of an input device. For example,the fall time and/or the rise time of the ramp signal and/or thefade-out time can be set manually by a person via the input device. Thismakes it possible to respond individually to special conditions.Furthermore, it is also possible that the fall time and/or the rise timeand/or the fade-out time can be predetermined by the microcontroller.The method can thus be used in a large number of different electricallyoperable motors or semiconductor bridges.

It has also proven to be advantageous if a first switching voltage ofthe ramp signal for the first controllable semiconductor switch and asecond switching voltage for the second controllable semiconductorswitch are monitored. As a result, it can be reliably checked in whichfunctional state or operating state the respective controllablesemiconductor switches are. As a result, the switching speed of thesemiconductor bridge can be increased, since the respective state of thesemiconductor switch is continuously known by means of the monitoring,and a short circuit can thereby be reliably prevented despite the fastswitching speed.

It is likewise advantageous if the control is performed by means of amicrocontroller, so that at least the pulse width modulation signal isprovided by the microcontroller. In particular, it can likewise beprovided that, in addition to the pulse width modulation signal, thefall time and/or the rise time and/or the fade-out time are alsocontrolled by means of the microcontroller. This allows reliable controlof the semiconductor bridge to be realized.

Another aspect of the invention relates to a control device. The controldevice is designed to carry out a method as claimed in one of thepreceding aspects or an advantageous embodiment thereof.

A still further aspect of the invention relates to an arrangement with acontrol device and with a semiconductor bridge with the two controllablesemiconductor switches and with the electrically operable motor and withthe microcontroller for generating the pulse width modulation signal.

According to an advantageous embodiment of the arrangement, the firstcontrollable semiconductor switch may be connected as a high-side switchand the second controllable semiconductor switch as a low-side switchand the first controllable semiconductor switch may be controllable bymeans of the ramp signal.

The invention also includes developments of the control device accordingto an aspect of the invention and the arrangement according to an aspectof the invention, which have features as have already been described inconnection with the developments of the method according to an aspect ofthe invention. For this reason, the corresponding developments of thecontrol device according to an aspect of the invention and of thearrangement according to an aspect of the invention are not describedagain here.

The control device and the arrangement have in this respect physicalfeatures that allow the method to be carried out or an advantageousembodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is described below. In thisrespect:

FIG. 1 shows a block diagram of an embodiment of an arrangementaccording to an aspect of the invention;

FIG. 2 shows a schematic voltage characteristic diagram; and

FIG. 3 shows a further schematic voltage characteristic diagram.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary embodiment explained below is a preferred embodiment ofthe invention. In the exemplary embodiment, the described components ofthe embodiment each represent individual features of the invention thatare to be considered independently of one another, which also developthe invention independently of one another and are therefore also to beregarded as part of an aspect of the invention individually or in acombination other than the one shown. Furthermore, the describedembodiment can also be supplemented by further features of aspects ofthe invention that have already been described.

In the figures, elements with the same function are each provided withthe same reference symbols.

FIG. 1 schematically shows an embodiment of an arrangement 1. Thearrangement 1 has a control device 2 and a microcontroller 3.Furthermore, the arrangement 1 has a semiconductor bridge 4, which inthe present case is formed by a first controllable semiconductor switch5 and a second controllable semiconductor switch 6. Furthermore, anelectrically operable motor 7, which can be controlled via thesemiconductor bridge 4, is connected to a node between the twocontrollable semiconductor switches 5, 6. In particular, a supplyvoltage V_(S) can be controlled via the semiconductor bridge 4. Theelectrically operable motor 7 is in particular an electrically operablemotor 7 of a motor vehicle. For example, the electrically operable motor7 may be an adjustment motor, which is used for example in a windowlifter or in a seat adjustment device. The electrically operable motor 7is in particular a direct current motor, so that the electricallyoperable motor 7 is operated with electrical energy in the form of adirect voltage as the supply voltage V_(S). Since, in particular in thecase of adjusting motors, the power must be regulated, in the presentexemplary embodiment the supply voltage V_(S) must be controlled bymeans of the semiconductor bridge 4 in accordance with the requiredpower for the electrically operable motor 7.

The first semiconductor switch 5 and the second semiconductor switch 6are designed in particular as MOSFETs or IGBTs. The first controllablesemiconductor switch 5 has a controllable first gate 13 and the secondcontrollable semiconductor switch 6 has a controllable second gate 14.In particular, it is provided that the controllable semiconductorswitches 5, 6 are closing switches, so that, when the gates 13, 14 arenot supplied, the controllable semiconductor switches 5, 6 are open andare therefore non-conductive.

It is likewise possible that the controllable semiconductor switches 5,6 are designed as make contacts, as a result of which the methodexplained below only changes on the basis of the corresponding parametervalues of the controls.

The first semiconductor switch 5 is connected in particular as ahigh-side switch and the second controllable semiconductor switch 6 isconnected in the present case in particular as a low-side switch. Inother words, the first controllable semiconductor switch 5 is connectedabove the load, in particular the electrically operable motor 7, and isthus connected between the supply voltage V_(S) and an electrical ground8. The second controllable semiconductor switch 6 is in particularconnected between the load, in other words the electrically operablemotor 7, and the electrical ground 8.

In the present exemplary embodiment, the control device 2 has acontroller 9, which is designed in particular to control thesemiconductor bridge 4. Furthermore, the control device 2 has a rampgenerator 10, by means of which a ramp signal 20 can be generated. Theramp generator 10 is supplied in particular via an additional rampvoltage between the supply points V_(R) and V₀. The additional rampvoltage may be for example 13 volts.

Furthermore, it may be provided that the control device 2 has a voltagefollower 11 for current amplification, by means of which the ramp signal20 of the ramp generator 10 can be amplified.

The control device 2 has in particular a first electrical output 12, thefirst electrical output 12 being coupled to the gate 13 of the firstcontrollable semiconductor switch 5 in the present exemplary embodiment.

The control device 2 also has a gate driver 15, by means of which thegate 14 of the second controllable semiconductor switch 6 can beactivated. In particular, a control voltage by means of which the secondswitchable semiconductor switch 6 can be activated may be provided atanother electrical output 16 by means of the gate driver 15.

Furthermore, it may be provided that the control device 2 has an inputdevice 17, which can be controlled manually by a person or by themicrocontroller 3. In particular, a fall time A1 and/or a rise time A2,which is in particular linear, of the ramp signal 20 and/or a fade-outtime A3 can be predetermined via the input device 17.

A pulse width modulation signal 18 can in particular be transmitted tothe controller 9 by means of the microcontroller 3. It is provided thatthe semiconductor bridge is controlled depending on the pulse widthmodulation signal 18, so that the electrically operable motor 7 can besupplied with the supply voltage V_(S) by means of the pulse widthmodulation signal 18.

A control signal 19 can in turn be transmitted from the controller 9 tothe ramp generator 10 depending on the pulse width modulation signal 18.In particular, the fall time A1 and/or the rise time A2 can be set inthe ramp generator 10 by means of the input device 17. The rampgenerator 10 in turn generates the ramp signal 20, which is sent to thevoltage follower 11, so that only a current amplification of the rampsignal 20 is carried out. The gate driver 15 can also be controlled bymeans of the controller 9 via a further control signal 19. Furthermore,it may be provided that the controller 9 has a monitoring device 21, bymeans of which a first switching voltage V₁ of the ramp signal 20 forthe first controllable semiconductor switch 5 and a second switchingvoltage V₂ for the second controllable semiconductor switch 6 can bemonitored.

In the case of the method according to an aspect of the invention forcontrolling the semiconductor bridge 4 for the electrically operablemotor 7, the semiconductor bridge 4 being provided with the firstcontrollable semiconductor switch 5 and the separate second controllablesemiconductor switch 6, the semiconductor bridge 4 is controlleddepending on the pulse width modulation signal 18 for supplying theelectrically operable motor 7 with electrical energy. It is providedthat, depending on the pulse width modulation signal 18, the ramp signal20 is generated with a predeterminable ramp slope 22 for controlling oneof the two controllable semiconductor switches 5, 6 by means of the rampgenerator 10. In the present example, it is provided in particular thatthe first controllable semiconductor switch 5 is controlled by means ofthe ramp signal 20.

FIG. 2 schematically shows a voltage characteristic diagram over time.In particular, in FIG. 2 the time t is plotted on the x axis A and thevoltage V in volts is plotted on a y axis O. FIG. 2 shows in particularthe characteristic of the ramp signal 20, which is dependent on thepulse width modulation signal 18. In the present FIG. 2, a first rampsignal 20 a with a ramp slope 22 and a second ramp signal 20 b with aramp slope 22 different from the first ramp signal 20 a are shown.

In the present case, the pulse width modulation signal 18 is designedfor example in such a way that it is designed as a square wave signalbetween 0 volts and 5 volts. For example, 5 volts can be interpreted aslogical 1 and 0 volts as logical 0. The voltage numbers in the presentexemplary embodiment are to be seen as purely by way of example and inno way conclusive. They only serve to illustrate the idea of an aspectof the invention.

At time t0, the pulse width modulation signal 18 has 5 volts, which canbe interpreted in particular as logical 1. In the present exemplaryembodiment, the ramp signal 20 has 22 volts. At time t1, the pulse widthmodulation signal 18 drops to 0 volts. The ramp signal 20 is thenlikewise “run down”. At time t2, the first ramp signal 20 a reaches the0 volt limit, which can be viewed in particular as an opening value, sothat an opening signal is shown for the first switchable semiconductorswitch 5, so that the first switchable semiconductor switch 5 opens. Attime t2′, the second ramp signal 20 b shown reaches the corresponding 0volt mark. In the present example, a negative voltage of 0.7 volts canbe seen on the ramp signal 20 a, 20 b, which on account of the diodevoltage is evident in the first switchable semiconductor switch 5. Thetime span between t1 and t2 or between t1 and t2′ corresponds to thefall time A1.

At time t3, the pulse width modulation signal 18 jumps from the logical0 to the logical 1 again. Since in particular the second controllablesemiconductor switch 6 only has to be opened at time t3 (see FIG. 3),the ramp signal 20 a, 20 b is correspondingly only applied to the firstcontrollable semiconductor switch 5 at time t4. The ramp signal 20 a, 20b is accordingly brought back to the voltage of 22 volts with the rampslope 22. At time t5, the first ramp signal 20 a again reaches 22 voltsand at time t5′ the second ramp signal 20 b again reaches 22 volts. Thetime between t4 and t5 or between t4 and t5′ corresponds to the risetime A2 of the ramp signal 20.

FIG. 3 shows a further schematic voltage characteristic diagram. Thetime t is plotted on the x axis A and the voltage in volts is plotted onthe y axis O. The voltage characteristics with respect to the pulsewidth modulation signal 18 and with respect to the ramp signal 20 areidentical to the representation from FIG. 2. The supply voltage V_(S) isshown as the voltage characteristic 23. After the pulse width modulationsignal 18 has dropped from the logical 1 to the logical 0 at the timet1, the supply voltage V_(S) drops in a ramp-like manner at the time t6on account of delay parameters at the first controllable semiconductorswitch 5. FIG. 3 also shows two voltage characteristics 23 a, 23 bcorresponding to the ramp signal 20 a, 20 b. In the present exemplaryembodiment, the voltage characteristic 23 a corresponding to the firstramp signal 20 a and the voltage characteristic 23 b corresponding tothe second ramp signal 20 b are shown. At time t7, the supply voltageV_(S) reaches 0 volts, the voltage characteristic 23 a or 23 b fallsfurther, to below 0 volts, on account of the diode voltages. At time t8,the second switchable semiconductor switch 6 is closed. In particular,the closing for the second controllable semiconductor switch 6 onlytakes place when the first controllable semiconductor switch 5 isclosed, which is at the time t2. The time span between t2 and t8 isreferred to as fade-out time A3, which can be predetermined as a safetymeasure, so that it can be reliably assumed that there is no shortcircuit. The same applies at times t2′ and t8′, which merely indicatethe difference between the voltage characteristics 23 a and 23 b. Thesecond switching voltage V₂ is represented in FIG. 3 by the voltagecharacteristic 24 or as the first voltage characteristic 24 a of thesecond switching voltage V₂ and the second voltage characteristic 24 bof the second switching voltage V₂.

At time t3, the pulse width modulation signal 18 is set from the logical0 to the logical 1 again. The voltage characteristic 24 drops at timet3, so that at a predetermined opening value, in particular 0 volts,after the voltage value has dropped at the second switchablesemiconductor switch 6 at time t9 and after a reaction time at time t4,the switching voltage V₁ is again ramped up at the gate 13 of the firstswitchable semiconductor switch 5 until it has reached full voltageagain at time t5 or t5′.

Overall, the example shows how a method and a system for controlling asemiconductor bridge 4 with a constant ramp slope 22 and without a shortcircuit can be provided by an aspect of the invention.

LIST OF DESIGNATIONS

-   -   1 Arrangement    -   2 Control device    -   3 Microcontroller    -   4 Semiconductor bridge    -   5 First controllable semiconductor switch    -   6 Second controllable semiconductor switch    -   7 Electrically operable motor    -   8 Electrical ground    -   9 Controller    -   10 Ramp generator    -   11 Voltage follower    -   12 First electrical output    -   13 Gate    -   14 Gate    -   15 Gate driver    -   16 Second electrical output    -   17 Input device    -   18 Pulse width modulation signal    -   19 Control signal    -   20 Ramp signal    -   20 a First ramp signal    -   20 b Second ramp signal    -   21 Monitoring device    -   22 Ramp slope    -   23 Characteristic of the supply voltage    -   23 a First characteristic of the supply voltage    -   23 b Second characteristic of the supply voltage    -   24 Second switching voltage    -   24 a First voltage characteristic of the second switching        voltage    -   24 b Second voltage characteristic of the second switching        voltage    -   V₁ First switching voltage    -   V₂ Second switching voltage    -   V_(S) Supply voltage    -   V_(R) Supply point    -   V₀ Supply point    -   A1 Descent time    -   A2 Rise time    -   A3 Fade-out time

The invention claimed is:
 1. A method for controlling a semiconductorbridge of an electrically operable motor, the semiconductor bridge beingcontrolled including a first controllable semiconductor switch and aseparate second controllable semiconductor switch for supplying theelectrically operable motor with electrical energy, the methodcomprising: outputting, by a controller, based on a pulse widthmodulation signal, a control signal to generate a ramp signal;generating, by a ramp generator, in response to the control signaloutput by the controller, the ramp signal with a predeterminable rampslope for controlling the first controllable semiconductor switch;applying, by the controller, the control signal to the secondcontrollable semiconductor switch; and applying, by the ramp generator,the ramp signal to the first controllable semiconductor switch, whereinthe predeterminable ramp slope is determined by the controller to ensurethat the first controllable semiconductor switch: closes after thesecond controllable semiconductor switch opens, and opens before thesecond controllable semiconductor switch closes.
 2. The method asclaimed in claim 1, wherein the ramp signal for a predetermined openingvalue represents an opening signal for the first controllablesemiconductor switch and a closing signal for the second controllablesemiconductor switch when the first controllable semiconductor switch isopen.
 3. The method as claimed in claim 2, wherein the ramp signal isgenerated by the ramp generator with a predetermined fall time, so thatthe closing signal for the second controllable semiconductor switch isat least only generated after the fall time.
 4. The method as claimed inclaim 3, wherein the closing signal for the second controllablesemiconductor switch is only generated after the fall time and after apredetermined fade-out time.
 5. The method as claimed in claim 1,wherein an opening signal for the second controllable semiconductorswitch is generated when there is a predetermined opening value of thepulse width modulation signal and a closing signal for the firstcontrollable semiconductor switch is generated when the secondcontrollable semiconductor switch is open.
 6. The method as claimed inclaim 5, wherein the ramp signal for the first controllablesemiconductor switch is generated with a predetermined rise time whenthe second controllable semiconductor switch is open.
 7. The method asclaimed in claim 1, wherein the ramp signal is amplified by a voltagefollower.
 8. The method as claimed in claim 1, wherein the fall timeand/or the rise time of the ramp signal and/or the fade-out time ispredetermined by an input device.
 9. The method as claimed in claim 1,wherein a first switching voltage of the ramp signal for the firstcontrollable semiconductor switch and a second switching voltage for thesecond controllable semiconductor switch are monitored.
 10. The methodas claimed in claim 1, wherein the pulse width modulation signal isoutput by a microcontroller to the controller.
 11. A control devicewhich is designed to carry out a method for controlling a semiconductorbridge of an electrically operable motor, the semiconductor bridge beingcontrolled including a first controllable semiconductor switch and aseparate second controllable semiconductor switch for supplying theelectrically operable motor with electrical energy, the control devicecomprising: a controller configured to output based on a pulse widthmodulation signal, a control signal to generate a ramp signal; and aramp generator configured to generate in response to the control signaloutput by the controller, the ramp signal with a predeterminable rampslope for controlling the first controllable semiconductor switch;wherein the controller is further configured to apply the control signalto the second controllable semiconductor switch, wherein the rampgenerator is further configured to apply the ramp signal to the firstcontrollable semiconductor switch, wherein the predeterminable rampslope is determined by the controller to ensure that the firstcontrollable semiconductor switch: closes after the second controllablesemiconductor switch opens, and opens before the second controllablesemiconductor switch closes.
 12. The control device as claimed in claim11, wherein the pulse width modulation signal is output by amicrocontroller to the controller.
 13. The control device as claimed inclaim 12, wherein the first controllable semiconductor switch isconnected as a high-side switch and the second controllablesemiconductor switch is connected as a low-side switch, and the firstcontrollable semiconductor switch is controlled by the ramp signal.